sqlite - driver not loaded

[Saurian]

Hello,

I'm using Qt to work with a sqlite database but I have an error. If I try to declare the handler for the QSqlDatabase object as a pointer I get the error: Driver not loaded. So if I use

QSqlDatabase db;
db = QSqlDatabase::addDatabase("QSQLITE");

QSqlDatabase db;
db = QSqlDatabase::addDatabase("QSQLITE");

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everything is ok but if I'm trying to use a pointer

QSqlDatabase *db;
db = new QSqlDatabase;
db ->addDatabase("QSQLITE");

QSqlDatabase *db;
db = new QSqlDatabase;
db ->addDatabase("QSQLITE");

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I get the error that the Driver is not loaded. Anyone has any idea why the second case doesn't work?

[d_stranz]

Have you deployed the SQL drivers into the appropriate subdirectory of your app directory, as specified in the docs?

[Saurian]

Well, I have no problem with the SQL driver for the first case (when I don't use a pointer) so I haven't changed the location for the SQL driver. But because I use a pointer you say I might need to have the dll file in the folder of my application?

[anda_skoa]

The second code snippet doesn't do anything with the return value of addDatabase().

Well, I have no problem with the SQL driver for the first case (when I don't use a pointer)

The first case also uses the initialized database connection returned by addDatabase() and stores it in the local variable.

Cheers,
_

[jefftee]

I get the error that the Driver is not loaded. Anyone has any idea why the second case doesn't work?

To elaborate on what @anda_skoa said:

QSqlDatabase::addDatabase is a static method and you are not operating on the db instance you think you are, because static member methods don't have a "this" pointer and thus do not operate on an instance of an object.

QSqlDatabase::addDatabase returns a QSqlDatabase instance, but you're not assigning that to a variable, so your attempt to add the database connection is essentially a no-op. You are creating a database instance by calling QSqlDatabase::addDatabase, then you throw away the result, hence the no-op.

The instance you allocated via "new QSqlDatabase()" is still an invalid database object since you have only invoked its default constructor.

If you *must* create a QSqlDatabase instance on the heap, try something like this:

QSqlDatabase *db = new QSqlDatabase(QSqlDatabase::addDatabase("QSQLITE"));

QSqlDatabase *db = new QSqlDatabase(QSqlDatabase::addDatabase("QSQLITE"));

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Good luck.